Effects of SiO 2 and B 2 O 3 on electrical properties of low-temperature sintered ZnO–Bi 2 O 3 varistors

This study utilized a conventional solid-state reaction method to prepare ZnO–Bi 2 O 3 –Sb 2 O 3 –Co 3 O 4 –Mn 3 O 4 –Nb 2 O 5 varistors sintered at low temperatures of 860 °C–880 °C. The effects of the different amounts of SiO 2 and SiO 2 -B 2 O 3 co-doping on the microstructure and varistor properties were investigated. The nonlinearity coefficient (α) increased from 51 for the sample without adding SiO 2 to 66 for the sample with 1.0wt% SiO 2 , and the breakdown voltage increased from 834 to 1260 V/mm. However, with excess SiO 2 addition, the α value gradually decreased from 66 for the sample with 1 wt% SiO 2 to 52 for the sample with 2.0 wt% SiO 2 , while the breakdown voltage continued to increase. Co-doping SiO 2 –B 2 O 3 improves liquid phase sintering due to the relatively low melting point of SiO 2 –B 2 O 3 –Bi 2 O 3 additives. The α value increased from 66 for the sample without adding B 2 O 3 to 83 for the sample with 2.0 wt% B 2 O 3 , while the breakdown voltage decreased from 1260 to 1120 V/mm. In comparison to higher temperature alternatives, the lower sintering temperatures (860 °C–880 °C) used in this study result in lower energy consumption during the manufacturing process. Because of their favorable cost-energy efficiency ratio, the SiO 2 –B 2 O 3 co-doped ZnO–Bi 2 O 3 varistors emerge as promising candidates for large-scale production.